With recent developments in electronics technology, reduction in size and increase in capacitance of monolithic ceramic capacitors have rapidly proceeded.
Outer electrodes are provided at both ends of a ceramic sintered body prepared by alternately laminating dielectric ceramic layers and inner electrode layers, and then firing the resulting laminate in this type of monolithic ceramic capacitor. By reducing the thickness of each of the dielectric ceramic layers and laminating a large number of such dielectric ceramic layers, a reduction in size and an increase in capacitance of the monolithic ceramic capacitor can be realized. However, when the thickness of each of the dielectric ceramic layers is decreased, the electric field applied to the dielectric ceramic layers increases. Accordingly, it is important that reliability under a high-temperature load be ensured. Monolithic ceramic capacitors with improved reliability have been actively developed.
For example, Patent Document 1 proposes a dielectric ceramic composition including main phase particles containing, as a main component, ABO3 (which represents a perovskite crystal wherein the A site contains Ba, or Ba and at least one of Ca and Sr, and the B site contains Ti, or Ti and at least one of Zr and Hf); a rare earth element R (wherein R represents at least one selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu); Mg; and Si, and secondary phase particles composed of a crystalline compound oxide containing the rare earth element R and Mg as main components; when some of the Ti of the B site is replaced with Zr, the relationship 0.06≦Zr/(Zr+Ti+Hf)≦0.40 is satisfied in terms of moles; and the contents of the rare earth element R, Mg, and Si relative to the content of ABO3 are in the range of 4% to 40%, in the range of 2% to 20%, and in the range of 2% to 15%, respectively, in terms of moles.
According to Patent Document 1, the insulation resistance of the dielectric ceramic composition can be maintained to be 100 kΩ or more, thereby ensuring reliability under a high-temperature load, even when an electric field of 16.6 kV/mm is applied at a high temperature of 125° C. for 1,000 hours, by allowing the secondary phase particles composed of the crystalline compound oxide containing the rare earth element R and Mg as main components to be present in the dielectric ceramic composition.
Patent Document 1: PCT Publication No. WO06/025205 pamphlet